I've fostered a dog that was fully trained as a service dog, but it was disqualified from being put into service because the vet found a hip dysplasia. The dog never pulled on its leash while I was walking it, and it immediately obeyed a bunch of commands (come, sit, heel, side, quiet, leave it, etc.) without the need for me to repeat. When I eventually got a dog of my own, I worked hard to train it because it was just so awesome to have a dog that was well behaved.

The last time I saw a "service dog" on a plane, it looked like it weighed about as much as its owner. As soon as the plane door opened after landing, the dog lunged toward the door, banging back and forth in the aisle. The owner could barely hold it back, and they weren't giving any commands to the dog. The flight attendant made a snarky comment, "What a wonderfully trained service animal!" I'm sure they know exactly how a genuine service animal behaves, and they are probably completely fed up with the widespread abuse of the service animal exemption.